.\"
.\" Copyright (c) 2025, Samsung Electronics Co., Ltd.
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.\" ufshci driver man page.
.\"
.\" Author: Jaeyoon Choi <j_yoon.choi@samsung.com>
.\"
.Dd July 17, 2025
.Dt UFSHCI 4
.Os
.Sh NAME
.Nm ufshci
.Nd Universal Flash Storage Host Controller Interface driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in the kernel configuration file:
.Bd -ragged -offset indent
.Cd "device ufshci"
.Ed
.Pp
Or, to load the driver as a module at boot, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
ufshci_load="YES"
.Ed
.Sh DESCRIPTION
Universal Flash Storage (UFS) is a low-power, high-performance storage
standard composed of a host controller and a single target device.
.Pp
The driver currently provides:
.Bl -bullet
.It
Initialization of the host controller and the target device
.It
Handling of UFS Interconnect (UIC) commands
.It
Support for UTP Transfer Requests (UTR) and UTP Task Management Requests (UTMR)
.It
Support for the SCSI command set
.It
Operation in the legacy single-doorbell queue mode
.It
Support for the PCI Express bus
.El
.Pp
After initialization, the controller is registered with the
.Xr cam 4
subsystem and its logical unit appears as the device node
.Pa /dev/daX .
.Pp
The driver is under active development; upcoming work includes full
UFS 4.1 feature coverage, additional power-management modes, and
ACPI/FDT-based attach support.
.Sh HARDWARE
The
.Nm
driver supports both host controllers and devices implementing the
Universal Flash Storage Host Controller Interface 4.1 and earlier.
.Sh CONFIGURATION
The
.Nm
driver currently operates with a single doorbell (one I/O-queue), so any
tunables that change the queue count are ignored.
When Multi-Circular Queue (MCQ) support is added and multiple queues
become available, the following queue count tunable values will take effect:
.Pp
To force a single I/O queue pair shared by all CPUs, set the following
tunable value in loader.conf(5):
.Bd -literal -offset indent
hw.ufshci.per_cpu_io_queues=0
.Ed
.Pp
To assign more than one CPU per I/O queue pair, thereby reducing the
number of MSI-X vectors consumed by the device, set the following tunable
value in loader.conf(5):
.Bd -literal -offset indent
hw.ufshci.min_cpus_per_ioq=X
.Ed
.Pp
To change the I/O command timeout value (in seconds), set the following tunable
value in loader.conf(5):
.Bd -literal -offset indent
hw.ufshci.timeout_period=X
.Ed
.Pp
To change the I/O command retry count, set the following tunable value in
loader.conf(5):
.Bd -literal -offset indent
hw.ufshci.retry_count=X
.Ed
.Pp
To force the driver to use legacy INTx interrupts, set the following tunable
value in loader.conf(5):
.br
(Note: until MCQ support is available the driver always uses legacy INTx, so
this value effectively remains 1)
.Bd -literal -offset indent
hw.ufshci.force_intx=1
.Ed
.Sh SYSCTL VARIABLES
The following controller-level
.Xr sysctl 8
nodes are currently implemented:
.Bl -tag -width indent
.It Va dev.ufshci.0.num_failures
(R) Number of command failures for the entire controller.
.It Va dev.ufshci.0.num_retries
(R) Number of command retries for the entire controller.
.It Va dev.ufshci.0.num_intr_handler_calls
(R) Number of times the interrupt handler has been called.
.It Va dev.ufshci.0.num_cmds
(R) Total number of commands issued by the controller.
.It Va dev.ufshci.0.timeout_period
(RW) Configured timeout period (in seconds).
.It Va dev.ufshci.0.cap
(R) Host controller capabilities register value.
.It Va dev.ufshci.0.num_io_queues
(R) Number of I/O-queue pairs.
.It Va dev.ufshci.0.io_queue_mode
(R) Indicates single doorbell mode or multi circular queue mode.
.It Va dev.ufshci.0.minor_version
(R) Host controller minor version.
.It Va dev.ufshci.0.major_version
(R) Host controller major version.
.It Va dev.ufshci.0.utmrq.num_failures
(R) Number of failed UTP task-management requests.
.It Va dev.ufshci.0.utmrq.ioq.num_retries
(R) Number of retried UTP task-management requests.
.It Va dev.ufshci.0.utmrq.num_intr_handler_calls
(R) Number of interrupt handler calls caused by UTP task-management requests.
.It Va dev.ufshci.0.utmrq.num_cmds
(R) Number of UTP task-management requests issued.
.It Va dev.ufshci.0.utmrq.cq_head
(R) Current location of the UTP task-management completion queue head.
.It Va dev.ufshci.0.utmrq.sq_tail
(R) Current location of the UTP task-management submission queue tail.
.It Va dev.ufshci.0.utmrq.sq_head
(R) Current location of the UTP task-management submission queue head.
.It Va dev.ufshci.0.utmrq.num_trackers
(R) Number of trackers in the UTP task-management queue.
.It Va dev.ufshci.0.utmrq.num_entries
(R) Number of entries in the UTP task-management queue.
.It Va dev.ufshci.0.ioq.0.num_failures
(R) Number of failed UTP transfer requests.
.It Va dev.ufshci.0.ioq.0.num_retries
(R) Number of retried UTP transfer requests.
.It Va dev.ufshci.0.ioq.0.num_intr_handler_calls
(R) Number of interrupt-handler calls caused by UTP transfer requests.
.It Va dev.ufshci.0.ioq.0.num_cmds
(R) Number of UTP transfer requests issued.
.It Va dev.ufshci.0.ioq.0.cq_head
(R) Current location of the UTP transfer completion queue head.
.It Va dev.ufshci.0.ioq.0.sq_tail
(R) Current location of the UTP transfer submission queue tail.
.It Va dev.ufshci.0.ioq.0.sq_head
(R) Current location of the UTP transfer submission queue head.
.It Va dev.ufshci.0.ioq.0.num_trackers
(R) Number of trackers in the UTP transfer queue.
.It Va dev.ufshci.0.ioq.0.num_entries
(R) Number of entries in the UTP transfer queue.
.El
.Sh SEE ALSO
.Xr cam 4 ,
.Xr pci 4 ,
.Xr disk 9
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 15.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was developed by Samsung Electronics and originally written by
.An Jaeyoon Choi Aq Mt j_yoon.choi@samsung.com .
.Pp
This manual page was written by
.An Jaeyoon Choi Aq Mt j_yoon.choi@samsung.com .
